1. For the position time graph, a - slope means you are going backwards. A 0 slope means you are standing still. A + slope means you are moving forward. When you cross the x axis it means you are behind your original starting point. That did not occur in our lab because we did not have too.
2. For the velocity time graph, a - slope means you are slowing down but still moving. A 0 slope means your speed is the same as what it was before. A + slope means you are increasing in speed. When you cross the x axis it means you are going backwards. That did not occur in our lab because the motion sensor could not detect us while we were behind it.